Probably the strongest "moral" in the play, if there is one, is related to the dramatic irony that comprises the powerful ending of the play. Unbeknownst to Romeo, Juliet has faked her own death; the note she sends to alert him of her plan never reaches him. However, news that she has died does reach him, and he returns to Verona, and breaks in to her family's burial crypt where he grieves for her loss and then commits suicide with his dagger. Within a short time, Juliet awakes from the potion induced sleep that created her "death," sees that Romeo has arrived, but is very recently dead ("thy lips are warm," she shrieks) and commits suicide for real this time.
Another theme one can take from this play is the destructive power of hatred. The hatred that exists between the Montagues and the Capulets ultimately costs Romeo, Juliet, and Romeo's best friend Mercutio, their lives. Ironically enough, these three young people were relatively uninvolved in, but still deeply affected by the feuding of the rival families. One might even speculate that it was the forbidden nature of the relationship because of the feud that made Romeo and Juliet not just fall in love, but become immediately obsessed with one another.